The present invention relates generally to printing machinery, such as printing presses, which may be used in various applications for applying inks, adhesives, and other liquid coatings to a surface. More particularly, the present invention relates to an improved arrangement for initially delivering and applying the ink, adhesive or other coating liquid to the printing machinery.
In flexographic printing, also known as aniline printing, the printing apparatus fundamentally comprises four basic cylindrical roller components; (a) a printing cylinder, commonly referred to as a plate cylinder, the circumferential peripheral of which carries flexible raised-surface printing plates, (b) an impression cylinder rotatable in peripheral surface contact with the plate cylinder for conveying a printable substrate, such as paper, in the nip region between the printing plates of the plate cylinder and the circumferential surface of the impression cylinder, (c) a cylindrical metering roller, commonly referred to as an anilox roller, having a circumferential periphery wetable with a printing ink or other printing liquid and arranged in peripheral surface contact with the plate cylinder for metered transfer of the printing liquid to the flexible printing places on the plate cylinder, and (d) a delivery device adapted for continually rewetting the peripheral surface of the anilox roller from a supply of the ink or other printing liquid.
One conventional form of known liquid delivery device is a so-called fountain roller device wherein a cylindrical roller rotates with its peripheral surface partially submerged in a reservoir of the printing liquid to maintain the surface constantly wetted with the liquid. Outside of the reservoir, the fountain roller rotates in peripheral contact with the anilox roller to continually transfer the printing liquid over the entire length and circumferential extent of the anilox roller for transfer, in turn, to the printing plates of the plate cylinder and therefrom to the printable substrate traveling over the impression cylinder. As will be appreciated, fountain roller delivery devices of this type apply an excess quantity of the printing liquid to the anilox roller, ordinarily requiring the provision of a wiping device, such as a so-called doctor blade, in contact with the peripheral surface of the anilox roller to remove excess printing liquid in advance of contact with and transfer to the printing plates of the plate cylinder. An alternative liquid delivery arrangement in conventional use replaces the fountain roller device with a dual doctor blade system wherein forwardly and reversely angle doctor blades are disposed in peripheral contact with the rotating anilox roller at circumferential spacings from one another so as to define between the doctor blades a liquid reservoir into which the printing liquid is continually supplied.
While each liquid delivery arrangement serves the intended purpose of insuring that the anilox roller and, in turn, the printing plates of the plate cylinder always remain fully wetted, thereby avoiding defects in the printing of the desired substrate from temporary or periodic starvation of the necessary printing liquid, the disadvantage created is the necessary provision for capturing and either recycling or disposing of the excess printing liquid inherently created. As a attendant result, equipment and operational cost are increased and environmental concerns (also with associated cost) must be addressed.